In general, a trolley for cable transportation system transportation units extends along a longitudinal axis, and comprises a frame and a clamp supported by the frame and configured to connect the trolley to the cable. The trolley comprises a first and a second guide, which are mounted projecting from opposite sides of the clamp. The guides are tapered towards their respective free ends, and have respective bottom faces configured to be arranged in contact with the cable and respective top faces configured to define a support for a roller unit (i.e., they act as rolling tracks for each roller of the roller unit when a trolley passes beneath a roller unit). Such guides are commonly called “lifter” and have the function of facilitating the passage of the clamp beneath a roller unit arranged in contact with the top part of the cable to define a curve with a center of curvature above the cable. In the case in point, the guide upstream, with reference to the direction of travel of the trolley, progressively raises the rollers of the roller unit to enable relatively easy passage of the clamp, while the guide downstream progressively accompanies the rollers in contact with the cable. The longer the guides, the more the movement of the rollers is progressive and without impact. However, the length of the guides negatively affects the storage capacity of the depots. It should be appreciated that during periods of inactivity of the cable transportation system, it is advisable to store the transportation units in a covered depot. In such depots, the transportation units are aligned along the longitudinal axes of the trolleys and arranged along purposely provided straight tracks.